A clone is the name for a group of organisms or other living matter with exactly the same genetic material. Genetic material consists of genes, the parts of cells that determine characteristics in living things. Many examples of clones exist in nature. In human beings and other higher animals, clones form naturally when identical twins or other genetically identical multiple births occur. Single-celled organisms, including bacteria, protozoa, and yeast, produce genetically identical offspring through asexual reproduction. These offspring develop from only one parent and are considered clones. Plants can also reproduce asexually through a process called vegetative propagation. In this process, a piece of root or stem can generate a new plant that is genetically identical to the donor plant. Vegetative propagation helps people obtain plant clones with desired traits. For example, farmers and breeders use this technique to develop apples with unique flavors or roses of certain colors. Hydras, flatworms, and other simple animals can be cloned through asexual reproduction or the process of regeneration. Recently, scientists have developed an experimental technique for cloning higher animals. This process first involves destroying the nucleus of an egg cell from the species to be cloned. A nucleus is then removed from a cell of an animal of the same species and injected into the egg cell. The egg, with its new nucleus, develops into an animal with the same genetic makeup as the donor. If a number of eggs receive transplants from the same donor, the offspring are considered clones of the donor animal. Scientists used this technique to clone such amphibians as frogs and salamanders as early as the 1950's. In 1996, a group led by British scientist Ian Wilmut used the procedure to clone a sheep. They named the clone "Dolly." The event marked the first time a mammal had been cloned in this way. Since the cloning of Dolly, scientists from Japan,...